The document discusses why software developers should use FlexUnit, an automated unit testing framework for Flex and ActionScript projects. It notes that developers spend 80% of their time debugging code and that errors found later in the development process can cost 100x more to fix than early errors. FlexUnit allows developers to automate unit tests so that tests can be run continually, finding errors sooner when they are cheaper to fix. Writing automated tests also encourages developers to write better structured, more testable and maintainable code. FlexUnit provides a testing architecture and APIs to facilitate automated unit and integration testing as well as different test runners and listeners to output test results.